Preheat your oven to 350°F (175°C) to ensure your muffins bake evenly.
Grease a muffin tin or line it with muffin liners to prevent sticking.
In a large mixing bowl, combine the mashed bananas, maple syrup, Greek yogurt, egg, whole milk, melted butter, and vanilla extract. Whisk until well blended.
In another bowl, mix together the flour, cocoa powder, baking soda, baking powder, and salt. Stir until combined.
Gradually add the dry ingredients to the wet mixture. Fold the ingredients together until just combined.
Gently fold in 1/2 cup of the chocolate chips, reserving the rest for topping.
Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full. Sprinkle remaining chocolate chips on top.
Bake in the preheated oven for 18-20 minutes, or until a toothpick comes out clean.
Let the muffins cool in the tin for 5 minutes before transferring to a wire rack.
